This invention relates to aqueous compositions that contain phenolic resins in combination with colloidal silica, silanes and water. In another aspect, this invention deals with the use of such compositions as coatings on solid substrates.
This invention falls generally into the class of colloidal silica based aqueous compositions which have been developed over the past fifteen years for use on certain substrates to prevent abrasion of the substrates or for corrosion protection of the substrates. There is always a need for a less expensive, more forgiving type of product, especially for use in the transparent glazing applications that include, for example, glazing for autos, buses and aircraft and vandal-proof windows in public buildings. The synthetic organic polymers useful in these applications, namely polycarbonate and acrylic polymers are easily fabricated into useful articles, such as glazing, but because of their low density, they are more subject to abrasion. Further, it appears as though this class of aqueous compositions have some utility in the protection of metal substrates, especially aluminum articles used in automotive decorative trim and aluminum articles used as decorative trim in modern homes.
As indicated supra, there are many aqueous compositions available in the prior art. For example, U.S. Pat. No. 3,986,997, issued Oct. 19, 1976 (Clark) discloses acidic dispersions of colloidal silica and hydroxylated silsesquioxanes in alcohol-water medium which are coated on plastic substrates and heat cured to give transparent abrasion resistant coatings. This same type of coating is disclosed in many other patents.
Also, these types of aqueous compositions have been modified with organic polymers in order to change the properties of the composition both as a storage liquid material and as a cured coating.
For example, Miyosawa, U.S. Pat. No. 4,016,129, issued Apr. 5, 1977 describes a hardenable coating composition which forms a transparent, flexible, hard and non-combustible coating which comprises an aqueous dispersion of silica and polyvinyl alcohol as a complex prepared by the reaction between colloidal silica dispersions and polyvinyl alcohol at a temperature about 50.degree. C. The reaction is allegedly accelerated by the presence of di- or trialkoxysilanes. These coatings appear to have less abrasion resistance than the inventive compositions.
Also, Miyosawa, in U.S. Pat. No. 4,330,446, issued May 18, 1982, describes a coating composition for metal surface treatment which contains colloidal silica, silane and organic polymer resins such as acrylics, alkyds, polyesters and epoxy-esters. These coatings when tested had low abrasion resistance (pencil hardness 2H) and most were not clear coatings.
Nason, in U.S. Pat. No. 2,182,208, issued Dec. 5, 1939, describes the preparation of a silicone modified non-aqueous phenolic resin by heating silicon esters or halides with phenol and formaldehyde in benzene. The benzene and by-produced alcohol were distilled away at reduced pressure. The residual resin is useful as a varnish. The silicon esters and silicon halides used were Si(OR).sub.4 and SiX.sub.a R'.sub.(4-a), respectively, where R is alkyl, R' is alkyl or aryl, X is halogen and a is the number of halogen atoms. A similar non-aqueous composition is described by Martin et al. in U.S. Pat. No. 2,707,191, issued Apr. 26, 1955. These compositions comprise the condensation reaction product of methylol benzene compounds and hydrolyzable silanes. This material, in a solvent solution, i.e. toluene, could be heat cured to a hard tack-free film.